Bowel Preparation for Patients Using Milk of Magnesia

Follow the instructions below to prepare for both your CT planning session (CT Simulation) AND radiation treatments:

Starting 3 nights before your appointment, take 2 tablespoons (tbsp) of Milk of Magnesia at bedtime. Do this each night at bedtime for 3 nights in a row. This should help you have a bowel movement (poo) the next morning.
Once treatment starts, keep taking Milk of Magnesia 1x per day, at bedtime, until your healthcare team tells you to stop. Let your healthcare team know when you starting having diarrhea (loose, watery poops).

If your appointment is after 2pm, take the Milk of Magnesia in the morning, making sure it is at least 6-8 hours before your appointment time. For example: if your appointment is at 2 p.m., you should take the Milk of Magnesia between 6 a.m. to 8 a.m. that morning.

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About This Resource

Author: Waterloo Wellington Regional Cancer Program

Revised: December 2025

PEM#: PEMWRHNCC0047

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Use this resource for your information only. It does not replace medical advice from your doctor or other healthcare professionals.

Email: [email protected]

Website: www.cancerwaterloowellington.ca

Bowel Preparation for Patients Using Milk of Magnesia

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